This invention relates to engine controls and more particularly to sensor apparatus for sensing the speed and direction of engine rotation and to control circuits associated with the sensor apparatus for controlling the operation of the engine in the event of reverse rotation of the engine or when preselected engine speeds are attained.
It is desirable to provide automatic controls for engines which operate when a particular engine speed has been reached. For example, governors are widely used to limit the maximum speed of an engine or to shut down the engine in case the maximum speed is exceeded. Another example involves the starting motor which cranks the engine at low speed on startup. When the engine catches and picks up speed the starting motor should be disengaged or deactivated to prevent damage thereto. Oftentimes it is desirable to provide warning devices which signal an engine malfunction, such as low oil pressure, which malfunction may be different in magnitude depending on whether the engine is operating above or below a selected speed.
At times, a slight rocking of the engine shaft can occur with normal stops and starts, so that the engine rotates in a reverse direction. It is highly desirable that reverse rotation be detected and that the engine be shut down in the event of such rotation for otherwise severe damage to the engine could result if ignition occurred with the engine turning in the reverse direction.
Various mechanical devices have been provided in the past which are directly connected to a rotating portion of the engine for movement thereby, these devices providing a means whereby the engine speed and direction of rotation may be monitored. Such devices, however, are subject to wear and fouling by dirt and grime. In addition, complicated linkages are necessary to provide for adjustments in the event that the critical speed at which a control function is to occur is changed.